#include <iostream>

using namespace std;

class Circle{
private:
    double r;
    static double a;
public:
    void setr(double r){
    this->r=r;
    }
    double getr() {
        return r;
    }
    void mianji(){
    double m;
    m=a*r*r;
    cout <<"mianji="<<m<<endl;
    }
    void zhouchang(){
    double z;
    z=2*a*r;
    cout <<"zhouchang="<<z<<endl;
    }
};

double Circle::a = 3.1415926;

int main()
{
    Circle rou1;
    rou1.setr(3);
    cout <<rou1.getr()<<endl;
    rou1.mianji();
    rou1.zhouchang();
    return 0;
}
